By Tom Dennis
Lesser Scaup, Aythya affinis
This week’s nature series features the Lesser Scaup, Aythya affinis, one of our most common diving ducks that is well known to hunters as the little bluebill or broadbill. This bird is common locally only during the winter and is difficult to distinguish from its close “cousin” the Greater Scaup. Read on for identification tips and clues on why this species likes the Blue Water Area.
We have reviewed other members of the genus Aythya which comes from Greek aithuia, an unidentified seabird; those being Redhead and Canvasback, both excellent divers. The species epithet affinis is Latin for “related to” for its resemblance to the Greater Scaup.
Adult male Lesser Scaup have a purple-black iridescent head with a small tuft at the back of the crown, yellow eye, black breast and tail, grey back with black barring, white flanks, and a blue-grey bill with a black tip. Females are a camouflaged version of the male with a brown head, amber eye, grey flanks, and a white band on the sides of the bill. Distinction of Lesser and Greater Scaup is easiest during flight during which the white wing bars show on the upper wing surface. The Lesser Scaup shows white only on the secondary wing feathers (approximately half of the wing closest the body) while the Greater show white into the primaries (wing feather near the wing tip). The head shape is another feature that differs and I like to compare the taller head of the Lesser Scaup to a “top hat” with a very evident tuft, whereas the Greater Scaup sports a more rounded “bowler”. Females show additional differentiation with the Lesser Scaup having an amber to orange eye and the Greater having a bright yellow iris. The white band on the Lesser Scaup female bill is usually much wider, especially at the top of the bill.
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Lesser Scaup breed from Alaska and the northern to central Canadian Provinces, south to the north-central United States and the upper edges of Lakes Superior and Huron where they prefer inland lakes, marsh ponds and protected bays. They travel in mixed flocks with Greater Scaup during migration however Lesser Scaup prefer freshwater habitat and winter in the lower great lakes and south as far Central America. Greater Scaup winter on both the Atlantic and Pacific seaboards.
These plentiful diving ducks with an estimated world population of three million individuals, have a diet of mainly mussels and clams that they forage from bottom mud. They have taken advantage of invasive Zebra Mussels and many now migrate relatively short distances due to the abundance of these mussels on the open winter waters along the St. Clair River. They also eat small fish, crustaceans, insect larvae, and water plants such as our abundant Wild Celery. Because they feed on mussels and clams that filter water, they can be susceptible to any pollutants and toxins that accumulate in these foods.
We often see Lesser Scaup at the Winter Bird Blast, jointly sponsored by Friends of the St. Clair River and Blue Water Audubon Society. The fifth annual popular event will be held on Saturday, February 23, 2019 and all ages are welcome to come learn and view this species and many other local winter birds. The indoor lesson is followed by an outdoor fieldtrip and it all starts at 9:00 AM at the Donald Dodge Auditorium in the St. Clair County Building in Port Huron. A fundraiser painting event is held from 1:00 – 3:00 PM at Studio 1219 where experts will help you create your very own masterpiece of the Common Goldeneye (advance registration required).
Tom Dennis is a free-lance writer, passionate birder, zoologist, and naturalist.